class Solution {
public:
    int firstUniqChar(string s) {
        vector<int> v(26);
        for (auto& x : s) ++v[x - 'a'];
        int res = INT_MAX;
        for (int i = 0; i < size(v); ++i)
        {
            if (v[i] == 1)
            {
                int pos = s.find(i + 'a');
                res = min(res, pos);
            }
        }
        return res == INT_MAX ? -1 : res;
    }
};